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LOANS HELD FOR INVESTMENT, NET - Credit Quality Indicators (Details) - USD ($) $ in Thousands | Mar. 31, 2022 | Dec. 31, 2021
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Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | $ 9,249,849 | $ 9,244,661
2022 | 493,979 |
2021 | 1,817,960 | 1,839,501
2020 | 1,389,448 | 1,502,001
2019 | 1,217,009 | 1,289,329
2018 | 696,107 | 726,725
2017 and Prior | 2,945,539 | 878,430
2016 and Prior |  | 2,356,918
Revolving | 632,210 | 588,432
Revolving-Term | 45,390 | 46,426
Total Loans | 9,237,642 | 9,227,762
Pass |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2022 | 489,398 |
2021 | 1,806,517 | 1,828,115
2020 | 1,365,302 | 1,473,478
2019 | 1,106,603 | 1,174,655
2018 | 568,972 | 606,030
2017 and Prior | 2,595,993 | 752,529
2016 and Prior |  | 2,114,512
Revolving | 606,532 | 552,538
Revolving-Term | 29,410 | 29,902
Total Loans | 8,568,727 | 8,531,759
Special Mention |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2022 | 4,581 |
2021 | 5,289 | 6,003
2020 | 14,051 | 15,891
2019 | 51,769 | 54,365
2018 | 26,016 | 21,926
2017 and Prior | 62,273 | 23,775
2016 and Prior |  | 45,900
Revolving | 10,157 | 4,071
Revolving-Term | 2,091 | 2,033
Total Loans | 176,227 | 173,964
Substandard |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2021 | 5,658 | 4,833
2020 | 10,095 | 11,011
2019 | 49,734 | 50,235
2018 | 100,344 | 97,994
2017 and Prior | 276,343 | 91,019
2016 and Prior |  | 196,506
Revolving | 15,521 | 30,823
Revolving-Term | 13,889 | 14,491
Total Loans | 471,584 | 496,912
Doubtful |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2021 | 496 | 550
2020 |  | 1,621
2019 | 8,903 | 10,074
2018 | 775 | 775
2017 and Prior | 10,930 | 11,107
Revolving |  | 1,000
Total Loans | 21,104 | 25,127
Total real estate loans |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 8,316,633 | 8,294,204
One-to-four family residential and cooperative/condominium apartment |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 669,099 | 669,282
2022 | 54,932 |
2021 | 128,132 | 129,679
2020 | 77,562 | 89,096
2019 | 66,898 | 82,568
2018 | 69,590 | 76,726
2017 and Prior | 209,761 | 80,365
2016 and Prior |  | 145,946
Revolving | 49,414 | 50,724
Revolving-Term | 12,810 | 14,178
Total Loans | 669,099 | 669,282
One-to-four family residential and cooperative/condominium apartment | Pass |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2022 | 54,932 |
2021 | 128,132 | 129,679
2020 | 76,520 | 86,028
2019 | 65,332 | 80,195
2018 | 68,429 | 75,354
2017 and Prior | 193,054 | 77,829
2016 and Prior |  | 129,276
Revolving | 48,569 | 49,878
Revolving-Term | 11,190 | 12,537
Total Loans | 646,158 | 640,776
One-to-four family residential and cooperative/condominium apartment | Special Mention |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2020 |  | 1,124
2019 | 334 | 335
2018 | 748 | 752
2017 and Prior | 1,810 | 334
2016 and Prior |  | 2,158
Revolving | 845 | 846
Revolving-Term | 742 | 747
Total Loans | 4,479 | 6,296
One-to-four family residential and cooperative/condominium apartment | Substandard |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2020 | 1,042 | 1,944
2019 | 1,232 | 2,038
2018 | 413 | 597
2017 and Prior | 14,897 | 2,202
2016 and Prior |  | 14,512
Revolving-Term | 878 | 894
Total Loans | 18,462 | 22,187
One-to-four family residential and cooperative/condominium apartment | Doubtful |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2018 |  | 23
Total Loans |  | 23
Multifamily residential and residential mixed-use |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 3,371,267 | 3,356,346
2022 | 235,590 |
2021 | 587,949 | 590,462
2020 | 342,620 | 353,747
2019 | 484,453 | 505,089
2018 | 176,769 | 183,616
2017 and Prior | 1,528,494 | 398,804
2016 and Prior |  | 1,309,248
Revolving | 14,567 | 14,555
Revolving-Term | 825 | 825
Total Loans | 3,371,267 | 3,356,346
Multifamily residential and residential mixed-use | Pass |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2022 | 235,590 |
2021 | 587,949 | 590,462
2020 | 330,142 | 341,206
2019 | 426,898 | 455,277
2018 | 134,833 | 151,226
2017 and Prior | 1,300,004 | 332,749
2016 and Prior |  | 1,145,609
Revolving | 14,567 | 12,277
Revolving-Term | 825 | 825
Total Loans | 3,030,808 | 3,029,631
Multifamily residential and residential mixed-use | Special Mention |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2020 | 10,985 | 11,040
2019 | 22,251 | 14,486
2018 | 4,216 |
2017 and Prior | 29,032 | 11,817
2016 and Prior |  | 26,252
Total Loans | 66,484 | 63,595
Multifamily residential and residential mixed-use | Substandard |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2020 | 1,493 | 1,501
2019 | 35,304 | 35,326
2018 | 37,720 | 32,390
2017 and Prior | 199,458 | 54,238
2016 and Prior |  | 137,387
Revolving |  | 2,278
Total Loans | 273,975 | 263,120
Commercial real estate ("CRE") |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 3,946,918 | 3,945,948
2022 | 166,352 |
2021 | 874,382 | 882,483
2020 | 803,263 | 851,450
2019 | 561,723 | 575,675
2018 | 362,875 | 370,839
2017 and Prior | 1,125,632 | 341,690
2016 and Prior |  | 874,439
Revolving | 46,693 | 43,183
Revolving-Term | 5,998 | 6,188
Total Loans | 3,946,918 | 3,945,947
Commercial real estate ("CRE") | Pass |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2022 | 166,352 |
2021 | 864,565 | 872,049
2020 | 800,777 | 848,694
2019 | 525,522 | 529,182
2018 | 298,706 | 306,360
2017 and Prior | 1,038,627 | 298,904
2016 and Prior |  | 815,238
Revolving | 46,693 | 43,183
Revolving-Term | 5,998 | 6,188
Total Loans | 3,747,240 | 3,719,798
Commercial real estate ("CRE") | Special Mention |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2021 | 5,289 | 6,003
2020 | 881 | 1,024
2019 | 28,819 | 39,305
2018 | 18,877 | 18,983
2017 and Prior | 30,315 | 11,039
2016 and Prior |  | 17,438
Total Loans | 84,181 | 93,792
Commercial real estate ("CRE") | Substandard |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2021 | 4,528 | 4,431
2020 | 1,605 | 1,732
2019 | 7,276 | 7,082
2018 | 45,292 | 45,496
2017 and Prior | 56,690 | 31,747
2016 and Prior |  | 41,763
Total Loans | 115,391 | 132,251
Commercial real estate ("CRE") | Doubtful |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2019 | 106 | 106
Total Loans | 106 | 106
Acquisition, development, and construction |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 329,349 | 322,628
2022 | 8,648 |
2021 | 160,508 | 142,123
2020 | 64,407 | 77,427
2019 | 40,083 | 56,885
2018 | 33,283 | 36,956
2017 and Prior | 6,263 | 6,809
2016 and Prior |  | 774
Revolving | 14,997 | 1,066
Revolving-Term | 1,160 | 588
Total Loans | 329,349 | 322,628
Acquisition, development, and construction | Pass |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2022 | 8,648 |
2021 | 159,843 | 142,123
2020 | 64,407 | 76,259
2019 | 40,083 | 56,885
2018 | 19,783 | 23,456
2017 and Prior | 6,263 | 6,809
2016 and Prior |  | 774
Revolving | 14,997 | 1,066
Revolving-Term | 1,160 | 588
Total Loans | 315,184 | 307,960
Acquisition, development, and construction | Special Mention |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2020 |  | 1,078
Total Loans |  | 1,078
Acquisition, development, and construction | Substandard |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2021 | 665 |
2020 |  | 90
2018 | 13,500 | 13,500
Total Loans | 14,165 | 13,590
Commercial and Industrial ("C&I") Loans |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 921,009 | 933,559
2022 | 28,457 |
2021 | 66,989 | 94,754
2020 | 101,596 | 130,281
2019 | 63,852 | 69,112
2018 | 53,590 | 58,588
2017 and Prior | 75,389 | 50,762
2016 and Prior |  | 26,511
Revolving | 506,539 | 478,904
Revolving-Term | 24,597 | 24,647
Total Loans | 921,009 | 933,559
Commercial and Industrial ("C&I") Loans | Pass |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2022 | 23,876 |
2021 | 66,028 | 93,802
2020 | 93,456 | 121,291
2019 | 48,768 | 53,116
2018 | 47,221 | 49,634
2017 and Prior | 58,045 | 36,238
2016 and Prior |  | 23,615
Revolving | 481,706 | 446,134
Revolving-Term | 10,237 | 9,764
Total Loans | 829,337 | 833,594
Commercial and Industrial ("C&I") Loans | Special Mention |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2022 | 4,581 |
2020 | 2,185 | 1,625
2019 | 365 | 239
2018 | 2,175 | 2,191
2017 and Prior | 1,116 | 585
2016 and Prior |  | 52
Revolving | 9,312 | 3,225
Revolving-Term | 1,349 | 1,286
Total Loans | 21,083 | 9,203
Commercial and Industrial ("C&I") Loans | Substandard |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2021 | 465 | 402
2020 | 5,955 | 5,744
2019 | 5,922 | 5,789
2018 | 3,419 | 6,011
2017 and Prior | 5,298 | 2,832
2016 and Prior |  | 2,844
Revolving | 15,521 | 28,545
Revolving-Term | 13,011 | 13,597
Total Loans | 49,591 | 65,764
Commercial and Industrial ("C&I") Loans | Doubtful |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
2021 | 496 | 550
2020 |  | 1,621
2019 | 8,797 | 9,968
2018 | 775 | 752
2017 and Prior | 10,930 | 11,107
Revolving |  | 1,000
Total Loans | 20,998 | 24,998
Other Loans |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 12,207 | 16,898
Other Loans | Credit Risk Profile |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 12,207 |
Other Loans | Performing |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | 16,533
Other Loans | Performing | Credit Risk Profile |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | 12,124 |
Other Loans | Non-Accrual |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding |  | $ 365
Other Loans | Non-Accrual | Credit Risk Profile |  |
Credit Risk Profile of Real Estate Loans [Abstract] |  |
Principal balances outstanding | $ 83 |

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